In recent years, a secondary battery, which can be charged and discharged, has been widely used as an energy source for wireless mobile devices. In addition, the secondary battery has attracted considerable attention as a power source for electric vehicles (EV), hybrid electric vehicles (HEV), and plug-in hybrid electric vehicles (Plug-in HEV), which have been developed to solve problems, such as air pollution, caused by existing gasoline and diesel vehicles using fossil fuels.
In addition, technology related to an electric power storage apparatus that stores electric power and stably supplies the stored electric power to a power system when needed has been developed. The electric power storage apparatus is an apparatus that stores electric power when electric power demand is low and supplies the stored electric power in case of overload or emergency. The electric power storage apparatus provides the effect of improving quality of electric power and energy efficiency. In particular, a market for a household electric power storage apparatus and a middle-sized industrial or commercial electric power storage apparatus has been rapidly expanding as the electric power storage apparatuses are related to smart grid technology.
Meanwhile, in order for a battery pack to provide output and capacity required by a predetermined apparatus or device, it is necessary for the battery pack to be configured to have a structure in which a plurality of unit cells or a plurality of battery modules, each of which includes a plurality of unit cells, is electrically connected to each other in series or in parallel. In addition, it is necessary for the battery pack to be configured to have a structure that is easily extendable and stable as the capacity of the battery pack is increased.
In particular, in a case in which a plurality of battery modules is used to constitute a battery pack, a plurality of members, such as bus bars and power cables, is needed for mechanical fastening and electrical connection between the battery modules, and a process of assembling the members is very complicated. In addition, in a case in which it is necessary to extend the battery pack, it is difficult to modify the structure of the battery pack. Furthermore, a plurality of components is additionally needed, which increases cost of manufacturing the battery pack.
In addition, since the battery pack is configured to have a structure including a plurality of battery modules, the safety and operation efficiency of the battery pack are considerably reduced when overvoltage, overcurrent, or overheat occurs in some of the battery modules. For this reason, it is necessary to provide a means to detect and control overvoltage, overcurrent, or overheat. For example, a safety system, such as a battery management system (BMS), is provided to detect overvoltage, overcurrent, or overheat and to cut off electric current of the battery pack or to operate a cooling apparatus based on the detected overvoltage, overcurrent, or overheat. In this case, however, various sensors and a plurality of wires are further needed in addition to the BMS, cost of manufacturing the battery pack is increased, and the process of manufacturing the battery pack is complicated.
In addition, the BMS is generally mounted in a battery pack case of the battery pack together with unit modules constituting the battery pack. When it is necessary to separate the BMS from the battery pack in order to perform required work, such as inspection, update, or replacement, for the BMS and then to mount the BMS in the battery pack case, it is difficult to perform the separating process or the mounting process since a plurality of component is complicatedly disposed in the battery pack case. Furthermore, the separating process or the mounting process are more complicated due to a plurality of cables, such as a power cable, a sensor cable, and a communication cable, connected to the BMS, and an accident may occur due to work errors during separating process or the mounting process.
Therefore, there is a high necessity for technology that is capable of fundamentally solving the above problems.